J’ai regardé Kraken, Binance et Bitfinex (que je ne connais pas) , seul Bitfinex donne quelques explications : "The minimum order sizes for each trading pair is periodically adjusted to maintain order sizes that are reasonably proportioned to their values. The ultimate goal is to keep the minimum order size between 10-25 USD equivalent value while limiting the changes to the minimum order sizes to useful incremental values."https://support.bitfinex.com/hc/en-us/articles/115003283709-What-is-the-minimum-order-size-

Hi there,
Eliah from the Kraken Client Engagement Team here. Thank you for your inquiry, I am certain we will be able to figure this out!
The minimum order amount for any asset pair is 0.01 units of the base currency of the pair. Base currency is the first of a currency pair. For example, in the currency pair XBT/USD, XBT is the base currency. Quote currency is the second of a currency pair. For example, in the currency pair XBT/USD, USD is the quote currency.
If you have any further questions or concerns, feel free to contact us.
Best regards,
Eliah,
Kraken Client Engagement

et

Hi again,
I had a further look into this and it appears that may have misunderstood our documentation. We use lot sizes to describe the volume of assets, and as such also minimum order sizes. You can obtain lot sizes for each asset pair via the API. See here: https://www.kraken.com/en-gb/help/api#get-tradable-pairs
When obtained, I think the minimum possible order size is 0.01 lot for each asset pair. Please let me know.
Best regards,
Eliah,
Kraken Client Engagement